The invention can find applications in many situations, and can, in particular, equip elderly persons and/or those with reduced mobility, isolated workers, children, animals . . .
In prior art, remote alarm systems are generally constituted of an assembly worn by the subject and linked to a fixed base, for example by an HF link. In the event of an abnormal situation, the fixed base transmits a coded message, carried for example by the telephone network, towards a specialised centre. In some institutions, the message can be carried by an internal network.
In all cases, these systems provide for an a posteriori and voluntary triggering of the process, following a fall or a malaise. This therefore assumes that the subject still has the ability and the will to do this.
A variety of remote alarm systems are known in prior art. In particular, portable devices exist under the form of a medallion around the neck, which requires a tightening or traction action to trigger an alarm. Apart from the fact that they are passive systems (requiring voluntary action from the wearer), these devices often produce false alarms, for example during the night, when they are worn and caught in the bedclothes. Furthermore, it is never known whether they are being worn or not.
Movement sensors are also known in prior art, providing information on abnormal nocturnal activity, or position sensor systems equipping beds in certain medical services.
In fact, in order to describe a fall, working from a person's centre of gravity, a cinematic has to be established, that means knowing the initial conditions (weight, height, position), the three accelerations and the three rotations. Such a solution is proposed in the French patent document FR-2760116 which uses two gyros. The trajectory is calculated and an inclinometer provides information about the end of the movement.
It can be carried in a pocket, but it still consumes a significant amount of energy, which is a factor limiting its use for a person in an isolated situation. Furthermore, it can only detect significant falls, and not a “micro-fall” on the patient's bed, or a slow fall, for example along a wall. But it is known that a dependent person, physically limited in movement, looks for supports along a path. Furthermore, in a sitting or lying-down position, a malaise will not be followed by an alarm.
Other systems are known in prior art associating the detection of deceleration at the moment of a fall and a two-directional vocal channel, systems associating protection relative to verticality and evaluation of the kinetic energy of the human body and systems associating an actimetry analysis with a position sensor.
In general, these different techniques are not 100% efficient, but only capable of detecting serious falls, with varying degrees of precision. They have two major inconveniences:                not all falls or malaises are systematically detected, especially when the subject is seated or lying down;        they produce a significant number of false alarms.        
Furthermore, non-ambulatory medical monitoring ensembles are known, able to transmit measurements of certain physiological parameters. The most sophisticated use telemedicine. These are complex and expensive systems, reserved for certain types of patients, but are not adapted to elderly persons and/or those with reduced mobility in isolated locations.
Yet again, other types of physiological sensors are known (pulse, breathing, temperature etc.) but they are never associated with decisional processes, and do not enable detection of an abnormal situation such as a fall.
The aim of the invention, in particular, is to overcome these different disadvantages of prior art.
More precisely, one aim of the invention is to provide a device and a method for detecting abnormal situations, particularly falls, with optimum reliability (meaning around 100%). In particular, the aim of the invention is to make it possible to detect all types of falls, even when the wearer of the device is in bed or sitting down, or with the body leaning against a wall.
Another aim of the invention is to provide such a device and such a process which can suppress, or at least greatly diminish, the production of false alarms (due, for example, to a sudden movement, or an inadvertent bang etc.).
In other terms, the aim of the invention is to make it possible to detect abnormal situations both more surely and more efficiently than known techniques.
Moreover, one aim of the invention is to provide such a device which:                is relatively simple and inexpensive to manufacture;        has low energy consumption, and therefore good autonomy;        is not cumbersome, but is ergonomic (meaning that it is not a nuisance for the wearer).        
These aims, as well as others which will become clear hereinafter, are attained according to the invention with the aid of a device for detecting abnormal situations, especially falls, in a living being, comprising means for generating an alarm signal representative of an abnormal situation, in function of an analysis of at least one item of activity information and, at least in certain cases, at least one item of physiological information.